ArtPlayer/packages/artplayer-plugin-danmuku/ARCHITECTURE.md

Danmuku maintenance map

The compatibility reference is the actual npm 5.3.0 package. Its archive, historical declarations, earlier exports and failure evidence are indexed in refactor/baselines/danmuku-release.json and danmuku-contract.md at the repository root. Do not infer runtime contracts from the old declaration file.

Module responsibilities

Module	Responsibility
src/index.js	Plugin factory, facade getters, bound methods, setting and heatmap composition
src/danmuku.js	Internal instance, method return identity, configuration/load commits, event and lifecycle wiring
src/config.js	Fresh defaults, validation schema, configuration comparison and normalization
src/input.js	Input forms, replacement ownership, independent append operations, cancellation and synchronous callback reentry
src/bilibili-parser.js	Pure legacy-compatible XML fields, mode mapping and entity decoding
src/bilibili.js	Fetch and response text, one parser Worker per request, fallback, settlement and Blob URL cleanup
src/scheduler.js	One RAF or asynchronous frame, cancellation generations, preparation ownership and failure recovery; DOM preparation moves to a renderer in PKG-DANMUKU-05
src/queue.js	Ordered state pools, eligibility and state transitions
src/worker-client.js	Track Worker lifecycle, a shared response dispatcher, unique request IDs and pending requests
src/worker.js	Track placement Worker; a separate protocol from the XML parser Worker
src/setting.js	Settings and emitter UI; lifecycle restructuring follows in PKG-DANMUKU-05
src/heatmap.js	Heatmap rendering; restructuring follows in PKG-DANMUKU-05

The package is undergoing staged migration. PKG-DANMUKU-03 separates input and configuration responsibilities in JavaScript; PKG-DANMUKU-04 separates scheduling and track requests; PKG-DANMUKU-06 converts all owned modules and Worker messages to TypeScript and validates installed consumers. This intermediate structure is not the final TypeScript or release acceptance.

Contracts to retain

• The registrar returns its facade synchronously. emit() and load() return Promises resolving to the internal Danmuku instance, which differs from that facade. config/hide/show/reset return that same internal instance synchronously; mount() returns undefined. Keep the three live getters.
• load() and load(undefined) replace only after input succeeds. load(target) appends without updating option.danmuku. Independent appends may complete in either order and can append after a replacement.
• Arrays enter synchronously. Empty initial input emits show -> config -> reset -> loaded before registration returns. Nonempty input inserts the first item before the first await, then awaits each emit() in order. A later invalid item leaves earlier accepted items present.
• A new replacement supersedes an older replacement. Destroy cancels all input operations. Cancelled public loads resolve to the same internal instance; they do not emit late loaded/error events or write stale rows. The input Promise itself may be uncancellable; observe its eventual rejection locally.
• Invoke a loader function without an explicit receiver. Invoke the filter through the current option so its receiver remains that option. Check load ownership again after callbacks and reset events, including synchronous callbacks that start another replacement.
• Keep input normalization observable: accepted objects receive missing mode, style and color before filtering, and the queue receives a shallow copy. Explicit time zero is preserved; missing time and NaN default to current time + 0.5. The historical validator accepts NaN as a number, so preserving zero must not accidentally remove that fallback. Positive infinity remains positive infinity; negative values, including negative infinity, clamp to zero.
• Function and Promise configuration changes use identity. Structurally equal ordinary values retain the historical JSON comparison behavior. Validate and normalize a prospective option before replacing the current option; invalid updates cannot corrupt it. Configuration does not implicitly reload input.
• Keep XML entity order, unpadded hexadecimal colors, numeric conversions, extension fields and existing mode mapping. An empty XML document is a valid empty result. Fetch/text failures must reach the public load's single error outlet and reject it; automatic initial loading observes that rejection.

Scheduling ownership

Keep at most one pending RAF or asynchronous preparation frame. Native play and playing both invoke the existing start path and retain its events, but must not create competing loops. Ready items precede wait items; wait selection retains the current-time +/- 0.1 second window and state-pool order. Keep the existing track algorithm and geometry fields until separately reviewed.

Pause, reset, successful replacement input commit, hide, seeking, destroy and replacing the beforeVisible callback invalidate unfinished preparation. Cancellation races the user Promise so an unresolved callback cannot prevent later work. A frame owns its allocated node; check that node identity before recycling it, and check the generation after each await or callback. Existing emit/stop nodes survive hide, seeking and callback changes; reset retains its explicit reset behavior.

Seek does not implicitly reset already displayed or paused comments. Date.now still measures wall-clock lifetime, excluding paused time. With synchronous playback enabled, new comments sample speed/playbackRate when allocated; active comments retain their assigned remaining seconds. Do not change these timing rules as incidental cleanup.

A rejected beforeVisible reports its original error once and excludes that item from further attempts in the current run. Explicit start, reset, an invalidation or replacement callback permits another attempt if the item is still eligible. False results retain their ordinary next-frame evaluation. Other items can continue after a rejection. Error-listener failures are observed locally and logged instead of creating a detached rejected RAF Promise.

A track Worker fault rejects its pending requests with the original error, disposes that Worker and reports one error, then halts internal scheduling. It does not fabricate a public stop event. A later start/reset rebuilds the Worker; repeated failure waits for another explicit recovery opportunity. Cancelled internal requests resolve { id, result: undefined } instead of remaining pending forever. Normal responses preserve { id, result }.

Recovery error listeners run synchronously and can call destroy, stop, reset, hide or start again. After recovery, the outer start must recheck destruction, stop and fault state, its cancellation generation and its start-attempt identity before continuing paused rows, scheduling or emitting start. Generation checks protect reset/hide and other invalidation; the attempt identity also protects a nested start that succeeds without changing the generation. Do not let the outer call revive stopped rows or add a second start event after a nested recovery. Ordinary repeated starts still retain their historical events and internal return identity. Recovery tests restore a working Worker factory before a single nested action; they do not manufacture an infinite retry loop.

Install the shared handler before sending requests. IDs are unique across requests and Worker replacement, including multiple requests in one millisecond. Late, unknown and duplicate replies do not settle a different request.

Verification and remaining work

yarn test:danmuku runs frozen historical contracts/failures and candidate input, parser, scheduler and Worker regressions. The historical helper and archives must remain frozen; candidate tests use test/helpers/danmuku-candidate.js and may select built artifacts through ARTPLAYER_DANMUKU_ARTIFACT. The input tests compare NaN and both infinities against frozen source and real npm main/legacy artifacts. Preserve those historical assertions alongside the explicit-zero correction when changing numeric normalization.

test/browser/danmuku-input.spec.js uses native video and Blob Workers against published and candidate cores. Run its source, main and legacy variants after the normal package build. Browser evidence distinguishes local XML/fault fixtures from the real Bilibili service, and Windows WebKit from Safari devices.

test/browser/danmuku-scheduler.spec.js verifies native callback cancellation, three modes, strict dense geometry, one request per prepared item, native pause/seek/rate and visible-node reuse. Preserve both geometric and protocol assertions; unique IDs alone do not prove non-overlapping tracks.

Settings cleanup, heatmap sampling and long-run load behavior still require PKG-DANMUKU-05/07. Check task evidence and the risk register before changing completion or release status; short native regressions are not package-wide stability acceptance.